Effective immediately, the extended BSD license that applied to the renderer has been removed and replaced by the LGPLv3.

There are multiple reasons for this change:

- use a commonly accepted license for this code
- eliminate any risk that my non-legalese additions to the old license may cause problems for anyone using this code
- use a license with very clear and explicit requirements about source code distribution.

So what does this mean?
For GZDoom itself it does not mean much. The LGPL explicitly allows integration into programs that are not compatible with the GPL.
Where it has some implications is forks that try to provide a GPL compatible subset of the code. With today's license change these forks MUST use the GPLv3 because the GPLv2 is not compatible with the LGPLv3. Read the license carefully what this may mean for you. The most important change is how to distribute the source code for any modified version. Again, carefully read the license text to see what the terms and conditions are. One thing that is not allowed is to provide the source only when requested - it must be directly obtainable by any end user